The present invention relates to improved photographic elements. More particularly, this invention relates to an improved lithographic printing plate which employs novel photosensitive compositions which are developable in aqueous developers.
Most photographic elements comprise a metal sheet substrate which is coated with a light sensitive diazonium compound in admixture with suitable binding resins, colorants, stabilizers, exposure indicators, surfactants, and the like.
While the art discloses a plethora of photosensitive compositions useful for lithographic purposes, their serviceability is limited by the need to develop them with solutions containing substantial amounts of organic solvents. This is undesirable since these solvents are costly and their effluent is environmentally harmful.
The present invention seeks to reduce or eliminate the need for such solvents in lithographic systems by providing a photographic element with a coating using a particular class of binding resins such that the exposed element is developable with a substantially aqueous based developer composition. Simultaneously the element shows no substantial attack to its image areas and the removed non-image area resins are substantially not re-deposited or re-adhered back onto the element after removal.
The invention also seeks to reduce the time necessary to effectively expose or insolubilize the coating by substantially increasing its light sensitivity while retaining high image resolution and extended press run performance.